1. Field of the Invention
The inventions relate to a cable assembly.
2. Description of Related Art
One concern in data communications is signal integrity. Factors that affect signal integrity include cable design and the process that is used to terminate or attach a cable. Cables are typically made of a plated center conductor covered by a dielectric and a braid or foil shield protector with an overall non-conductive jacket. The termination of the braid onto a device, such as a printed circuit board (PCB) or a connector, can significantly affect cable performance.
One way to terminate a braid is to strip the end of the braid and solder the end of the wire onto a PCB/connector termination. One popular method of soldering a wire onto a solder pad is hot bar soldering. One problem with this method in that a large amount of heat must be introduced during the solder. The heat causes the dielectric to melt and subsequently shrink. In addition, a significant amount of time is often consumed by this method. Finally, the solder pad, PCB, or connection material may burn when using hot bar soldering.
Laser terminating is another method of terminating a wire onto a PCB/connector, but it also has problems such as a tendency to burn and variable power. Also, the timing of the laser pulse needs to be within very tight tolerances.
Parallel gap resistance welding is another method of terminating a wire onto a PCB/connector. One problem with resistance welding is that it is very difficult, and sometimes impossible, to resistance weld a wire of 28 AWG or higher gage size. This is because a large amount of heat is necessary to weld a wire of that thickness, and the heat has a tendency to burn the solder pad on the PCB or the connection material.
However, parallel gap resistance welding has advantages over hot bar welding. There is no shrinking of the cable dielectric with parallel gap resistance welding, and the time needed to make the weld is significantly shorter than the time to solder.
A common way to terminate a braid is to use a ferrule. One significant problem with a ferrule is that crimping the wire to apply the ferrule tends to crush the cable dielectric. Another problem with existing methods of terminating a braid is that they can tend to rearrange the placement of the differential pair within the cable jacket. Both problems can affect impedance and other electrical parameters, which affect signal integrity.